Write down in four steps how to find out the focal length of a convex lens experimentally in the Lab.
1. Fix the convex lens on the lens holder or stand and place it place it on the
table near an open window of the laboratory.
2. Locate a distant tree/building from
the open glass window (if an open window is not available then obtain the image
of the window itself on the screen.
3. Place the screen behind the convex
lens.
4. Adjust the position of the convex
lens and the screen so that a sharp, inverted and diminished image of a distant
object is formed clearly on the screen.
5. Note the positions of the screen and
the convex lens stand with the help of measuring scale.
6. Find the distance between the optical
centre of the lens and the screen. This distance is equal to the focal length
of the convex lens. Record the the focal length.
7. Repeat the experiment a few times by
changing the positions of the convex lens stand and note the corresponding
changed position of the screen.
8. Calculate the mean value of the focal
length.
1. Fix the convex lens on the lens holder or stand and place it place it on the
table near an open window of the laboratory.
2. Locate a distant tree/building from the open glass window (if an open window is not available then obtain the image of the window itself on the screen.
3. Place the screen behind the convex lens.
4. Adjust the position of the convex lens and the screen so that a sharp, inverted and diminished image of a distant object is formed clearly on the screen.
5. Note the positions of the screen and the convex lens stand with the help of measuring scale.
6. Find the distance between the optical centre of the lens and the screen. This distance is equal to the focal length of the convex lens. Record the the focal length.
7. Repeat the experiment a few times by changing the positions of the convex lens stand and note the corresponding changed position of the screen.
8. Calculate the mean value of the focal length.
